234 University of California Publications in Zoology. [Vol. 6 



This consists of a ring or septum (fig. 2, sep.) which occurs 

 within the ooecium at the same place relatively where the flexible 

 joint (J.) does, which separates the basis rami from the distal 

 tubular portion of a zocecium. This septum is visible through 

 the calcareous wall of the ovicell, especially if the specimen is 

 slightly stained, or is simply cleared in glycerine, or oil. It 

 separates, as will readily be seen, the inflated portion of tKe 

 ovicell from the long conical portion (oe. a). After the septum 

 forms, section of the ovicell in any stage of growth shows that 

 it is formed in this species by a thickening of the inner chitinous 

 layer of the ocecial wall. This is shown in fig. 3, which represents 

 a section through the lower portion of a young ovicell. At some 

 distance below the embryo (e»ib.), the chitinous wall thickens 

 and grows inward forming a circular shelf (sep.). This chit- 

 inous shelf is broader and thicker in older ovicells (tig. 4. sep.) 

 but it seems never to close entirely. In all cases observed in this 

 species it does not form a continuous floor, but remains open in 

 the middle. In close connection with it. and with the cellular 

 tissue surrounding the embryo, a delicate chitinous tube, (chi. t.), 

 is seen extending, as shown in figs. 3 and 4, downward toward 

 the base of the ocecial cone. The position and mode of formation 

 of the septum relates it with the flexible joints of ordinary 

 zocecia, if not making the two structures homologous. The lower 

 portion of the ovicell. what I have called the ocecial cone, would 

 then be homologous with a basis rami, and the inflated portion 

 with the distal tubular part of the zocecium. 



In C. <ji niculata a similar structure is seen (tig. 7. s< /<.). This 

 in cross-section is seen to be formed in virtually the same manner 

 as in C. franciscana. The projecting shelf is thicker somewhat. 

 and from it there depends a delicate, chitinous tube more 

 apparent than is that of C. franciscana. Above the septum there 

 is an added structure in the form of a delicate, chitinous arch 

 continuous with the tissue of the tube and attached to the septum. 



If ('. edwardsiana is viewed in optical section, the same dark 

 ring is discernible as is seen in the two species just mentioned 

 i pi. in. tig. 10, si /(.). On investigation the darkening is found 

 to be due not to a thickening of the chitinous wall, but to a thick- 

 ening of the cellular wall. At the same point relatively at which 



